1. Field of the Invention
The present invention is directed to a track link for a track type vehicle. More generally, it is directed to a one piece track link assembly including parallel chains of track links connected end-to-end by link pins, with positive retention of the pins in the links.
2. Description of the Related Art
Tracks composed of parallel arranged chains of track links, connected end-to-end at overlapping inboard and outboard ends of the respective links, are well known for use with heavy equipment such as earth moving vehicles. Typically the links of each chain, and the parallel arranged chains of links, are connected by pivot joints comprised of link pins which are press fitted in bores at the outboard ends of corresponding links of each chain, and bushings rotatably mounted on the links and press fitted in the bores of the outboard ends of adjacent corresponding links of each chain. The bearing surfaces between the respective link pins and bushings are lubricated by a lubricating oil reservoir in the link pin, which is sealed by seal members having seal lips which bear against the ends of the respective bushings.
The link pins are press fit in their bores with high pressure in an effort to prevent outward movement of the respective links on the pins, which movement may occur as result of the working forces exerted on the track during the operation of the vehicle. Such movement, if present, causes the joints to become loose and develop what is commonly referred to as end play. End play is especially undesirable in chains having sealed link lubrication since it reduces seal pressures at the seal lips, which may permit the lubricant to leak past the seals and the ingress of abrasive materials. The loss of lubricant and the ingress of abrasive materials can lead to excessive wear and premature failure of the track.
Efforts have therefore been made to minimize end play in the track link assemblies. For example, in U.S. Pat. No. 4,222,616, gussets mounted to the track shoes bear against the ends of the pins and prevent their outward deflection. However, this requires the use of special track shoes.
U.S. Pat. No. 4,618,190 uses retainers formed in cavities of the links for preventing end play. However, appropriate grooves must be machined in both the pins and the links.
In U.S. Pat. No. 5,201,171, the outboard end collars of the links have pin bosses with bores through which the link pins extend. Nodules are mechanically formed in the pin bosses and protrude inwardly from the bores into grooves at the ends of the pins to prevent end play. However, such permanent deformation of the bosses makes it difficult to remove the pins from the links for repair and/or replacement. For example, it is common practice to disassemble the chain so that the bushings can be rotated 180.degree. to expose a new wear surface to the drive sprocket. This is very difficult in the case of the deformed link bosses of U.S. Pat. No. 5,201,171.
Snap rings have been used to retain link pins of specialized split link type track links, for example the Berco CR4659 split link used to connect end of a link track. However, they have never been used in regular links to prevent end play.